What are series?

Answer 1

A series circuit is when all the components are connected together in one continuous way, with no cross-connections between intermediate parts. If one component breaks the whole circuit is broken.

A good example of a series circuit is how all the low-voltage lights to go on a Christmas tree are usually connected in series in a "head to tail" fashion, so that the total voltage of the string of lights matches the house service voltage.
A circuit is said to be in series if

1. Its components are connected end to end.

2.same current flows through all the components,

3.voltages are additive,

4.powers are additive.